ASA 127th Meeting M.I.T. 1994 June 6-10

2pUW8. Mechanisms causing special features of ambient noise statistics in
shallow water.

Jacob George

Naval Res. Lab., Code 7176, Stennis Space Center, MS 39529

Special features of ambient noise statistics, distinct from signal
statistics, have been previously reported [J. Acoust. Soc. Am. 94, 1820(A)
(1993)]. A possible mechanism for these features had been identified through
simulation and from normal mode theory as depth fluctuations of a noise source
close to the surface. Since then, the cumulative effect of multiple sources of
this kind has been investigated following the techniques used by Dyer in
analyzing distant shipping noise [J. Acoust. Soc. Am. 53, 564 (1973)]. The
results show that while a single source assumption does fit experimental
results, assumption of multiple sources does not. Because several merchant
ships were known to be present during the data collection, it is unlikely that
ambient noise was dominated by a single source. This suggests that additional
mechanisms such as wind-generated noise may also be responsible for the
observed features. The usefulness of the single source formula as an empirical
fit to data, and as an important potential contributor to the observed
statistical features will be discussed. [Work supported by ONR, with technical
management provided by NRL/SSC.]